FR3088057A1 - ASSEMBLY CONSTITUTING AN ACOUSTIC INSULATOR - Google Patents

Abstract

The invention relates to an assembly (100) constituting an acoustic insulator and comprising a first plate (102), a second plate (104) pierced, a plurality of first structures and second structures (112). Each first structure (110) consists of first and second strips (250, 252), where each is shaped to form half of the wall of a cage (202) and where for two successive halves, each strip (250, 252) has a side of a junction wall (207). Each second structure (112) consists of first and second strips (350, 352), where each is shaped to form half of the wall of a cone (302), where for each strip (350, 352), at least one of the wall halves of each cone (302) is pierced, and where for two successive halves, each strip (350, 352) has a section of the connecting wall (307). Each cone (302) is located in a cell (205) and each connecting wall (307) is located between the two sides of a junction wall (207), and where between two adjacent first structures (110), a second structure (112) is also put in place. Such an assembly makes it possible to obtain attenuation of several acoustic frequencies and is easy to manufacture.

Description

Description

Title of the invention: ASSEMBLY CONSTITUTING AN ACOUSTIC INSULATOR

Technical Field [0001] The present invention relates to an assembly constituting an acoustic insulator, as well as to a method of manufacturing such an assembly.

PRIOR ART [0002] During operation, an aircraft engine generates noise. This engine is housed in a nacelle and to reduce this noise, it is known to install assemblies constituting an acoustic insulator around the engine in the structure of the nacelle.

[0003] Such assemblies constituting an acoustic insulator take, for example, the form of honeycomb structures. Such a honeycomb structure comprises two parallel plates, one of which is perforated and between which are arranged hexagonal cells juxtaposed to each other.

It is also known in other applications to use truncated cones which are placed in cavities.

[0005] Although from an acoustic point of view, such assemblies give good results, it is desirable to find an assembly constituting an acoustic insulator which makes it possible to attenuate a certain number of acoustic frequencies and which is easy to manufacture.

SUMMARY OF THE INVENTION An object of the present invention is to provide an assembly constituting an acoustic insulator which can attenuate a certain number of acoustic frequencies and which is easy to manufacture.

To this end, an assembly is proposed constituting an acoustic insulator and comprising a first plate, a second plate pierced with holes, a plurality of first structures arranged next to each other in a second direction, and a plurality of second structures arranged side by side in the second direction, where each first structure comprises a succession of cages, each delimiting a cell having a section of a shape, and between two adjacent cages, a junction wall made up of two sides distant from each other, where each second structure comprises a succession of hexagonal cones, each having a base and an apex, and between two neighboring cones, a connecting wall made up of two sides, where the base has a section of the same shape as the section of the cells, where each first structure consists of a first strip and a second strip arranged opposite one on the other and extend between the first plate and the second plate, where for each cage, the first strip is shaped to form half of the wall of said cage and the second strip is shaped to form the other half of the wall of said cage, and where for two successive halves, each strip has a section of the junction wall which connects two consecutive halves, where each second structure consists of a first strip and a second strip arranged facing each other and extend between the first plate and the second plate, where for each cone, the first strip is shaped to form half of the wall of said cone and the second strip is shaped to form the other half of the wall of said cone, where for each strip, at least one of the wall halves of each cone is pierced with a hole, and where for two successive halves, each strip has a section of the connecting wall which connects two consecutive halves, [0012] d e so that each cone is in a cell and each connecting wall is between the two sides of a junction wall, and where between two first neighboring structures, a second structure is also put in place.

Such an assembly makes it possible to obtain attenuation of several acoustic frequencies and is easy to manufacture.

Advantageously, at least one cone is asymmetrical, so that the volumes of the two chambers created between said cone and the wall of the cage where it is housed are different.

Advantageously, at least one of the ends of the strips has holes. According to a particular embodiment, the shape is a hexagon, each half of the wall of a cage is made up of three successive sides, and each half of the wall of a cone is made up of three successive sides.

According to another particular embodiment, the shape is a circle, each half of the wall of a cage consists of a half-cylinder, and each half of the wall of a cone consists of a half-cone of revolution.

The invention also provides a method of manufacturing an assembly according to one of the preceding variants, comprising:

- a first step during which a first strip of the second structure is fixed to a first strip of the first structure, [0020] - a second step during which a second strip of the second structure is fixed to the first strip of the second structure thus fixed, [0021] - a third step during which a second strip of the first structure is fixed to the second strip of the second structure thus fixed, [0022] - as long as a first structure or a second structure must be added, a looping step on the first step considering that the second strip of the first structure thus fixed constitutes the first strip of the following first structure, [0023] - a step during which, the first and second structures thus fixed are fixed between the first plate and the second plate.

Brief Description of the Drawings The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in relation to the drawings seals, among which:

[Fig.l] is a perspective view of an assembly constituting an acoustic insulator according to a first embodiment of the invention, [fig26] is a perspective view of a first structure of the acoustic insulation of the Eig.

1.

[Fig.3] is a perspective view of a second structure of the acoustic insulation of the Lig. 1, and [fig.4] is a perspective view of an assembly constituting an acoustic insulator according to a second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS [0030] La Eig. 1 shows an assembly 100 constituting an acoustic insulator according to a first embodiment of the invention. The assembly 100 comprises a first plate 102 and a second plate 104 which are at a distance from each other. One of the plates, here the second plate 104, is pierced with holes 106 to allow the passage of the acoustic waves.

Between the first plate 102 and the second plate 104, are arranged a plurality of first structures 110 and a plurality of second structures 112.

The Eig. 2 shows the first structure 110 and the Eig. 3 shows the second structure 112.

The first structure 110 forms a honeycomb structure which comprises a succession of cages 202 extending in a first direction 201, forming a line, and in the assembly 100, the first structure 110 repeats in a second direction 203 perpendicular to the first direction 201, thus forming columns. Each cage 202 is hollow and has a wall with a hexagonal and hexagonal section 204 parallel 2 to 2. Each cage 202 delimits a cell

205 hexagonal.

On a line, each cage 202 is attached to each neighboring cage 202 by a junction wall 207 which is parallel to the first direction 201. Each junction wall 207 of the first structure 110 is double and therefore consists of two parallel sides. The two sides of the junction wall 207 are spaced from each other to allow the introduction of a connecting wall 307 of the second structure 112 as explained below.

In the second direction 203, the cages 202 are arranged one against the other in staggered rows and two adjacent cages 202 have a common pan 204. In addition, each junction wall 207 of a line forms one of the flaps 204 of the cage 202 of the neighboring line.

The sides 204 and the junction walls 207 extend between a first end 113 secured to the first plate 102 and a second end 114 secured to the second plate 104. The ends 113 and 114 are fixed to the first plate 102 and the second plate 104, for example by gluing, welding or the like.

For a line, the first structure 110 consists of a first strip 250 and a second strip 252, which are arranged opposite one another and extend between the first plate 102 and the second plate 104.

For each cage 202, the first strip 250 is shaped to form half of the wall of said cage 202 in the form of three successive sides 204 and the second strip 252 is shaped to form the other half of the wall of said cage 202 in the form of three other successive sections 204 of said cage 202.

For two successive half-hexagons, each strip 250, 252 has a section of the junction wall 207 which connects two consecutive half-hexagons.

The second structure 112 comprises a succession of cones 302 extending in the first direction 201 and in the assembly 100, the second structure 112 repeats in the second direction 203.

The base of each cone 302 has a hexagonal section and is positioned between the two strips 250 and 252 of the first structure 112 at the second end 114 while the top of each cone 302 comes into contact with the first plate 102. Each cone 302 forms a hexagonal cone with a hexagonal wall 304. The hexagonal base has the dimensions appropriate to those of the cell 205 so that it can be accommodated therein.

On a line, each cone 302 is separated from its neighbor by a connecting wall 307 which is parallel to the first direction 201. Each connecting wall 307 is double and therefore consists of two parallel and integral sides.

Each cone 302 is positioned in a cell 205 and the connecting wall 307 is positioned between the sides of the junction wall 207.

For a line, the second structure 112 consists of a first strip 350 and a second strip 352, which are arranged opposite one another and extend between the bases and the tops of the cones 302, that is to say between the first plate 102 and the second plate 104.

For each cone 302, the first strip 350 is shaped to form half of the wall of said cone 302 in the form of three successive sections 304 of said cone 302 and the second strip 352 is shaped to form the other half of the wall of said cone 302 in the form of the three other successive faces 304 of said cone 302.

For two successive half-cones, each strip 350, 352 comprises a section of the connecting wall 307 which connects two consecutive half-cones.

For each strip 350, 352, at least one of the wall halves of each cone 302 is pierced with a hole 354 for the passage of acoustic waves, that is to say here at least one sections 304.

Thus, on a line in the first direction 201, in each cell 205 of the first structure 110 is disposed a cone 302 of the second structure 112. As the connecting walls 307 extend from a cell 205 to the other, the volume between the cone 302 and the wall of the cage 202 where said cone 302 is housed, is divided into two separate chambers 150 and 152.

In addition, between two first neighboring structures 110 in the second direction 203, a second structure 112 is also put in place. The first two neighboring structures 110 are spaced from one another to allow the passage of the connecting walls 307.

Such an assembly 100 thus constitutes an acoustic insulator which combines the quarter-wave principle and a Helmholtz resonator. The interior of each cone 302 attenuates the high frequencies, and the chambers 150 and 152 attenuate the low frequencies. In addition, it is possible to make asymmetric cones 302 so as to obtain chambers 150 and 152 of different volumes in order to attenuate two different low frequencies.

In addition, such an assembly 100 is easy to perform.

Depending on the materials used, each strip 250, 252, 350, 352 can be produced by stamping, thermoforming or folding, then fixed by any suitable means, welding, bonding ...

In addition, the densities and thicknesses of the strips 250, 252, 350, 352 can be different in order to have a balance between the mechanical strength of the assembly 100 and the flexibility for forming for the strips.

The assembly principle consists in fixing a first strip 350 of the second structure 112 to a first strip 250 of the first structure 110, then in fixing a second strip 352 of the second structure 112 to the first strip 350 of the second structure 112 thus fixed, then fixing a second strip 252 of the first structure 110 to the second strip 352 of the second structure 112 thus fixed.

The process continues in the same way, considering that the second strip 252 of the first structure 110 thus fixed constitutes the first strip 250 of the following first structure 110.

The manufacturing and assembly process is therefore simple and implements simple steps.

The assembly is then fixed between the first plate 102 and the second plate 104.

The manufacturing process for assembly 100 thus comprises:

- a first step during which a first strip 350 of the second structure 112 is fixed to a first strip 250 of the first structure 110, [0060] - a second step during which a second strip 352 of the second structure 112 is fixed to the first strip 350 of the second structure 112 thus fixed, a third step during which a second strip 252 of the first structure 110 is fixed to the second strip 352 of the second structure 112 thus fixed, as long as a first structure 110 or a second structure 112 must be added, a looping step on the first step, considering that the second strip 252 of the first structure 110 thus fixed constitutes the first strip 250 of the following first structure 110, a step during which the first and second structures 110, 112 thus fixed are fixed between the first plate 102 and the second plate 104.

When fixing between the first plate 102 and the second plate 104, the first ends 113 and the tops of the cones 302 are fixed to the first plate 102, and the second ends 114 and the bases of the cones 302 are fixed to the second plate 104.

To take into account the curvature when the assembly 100 must be put in place against an arcuate part such as for example an air inlet, an acoustic plug for a turbomachine nozzle, etc. The strips 250, 252, 350 and 352 are assembled to each other directly on a tool incorporating the arcuate shape corresponding to said arcuate part. That is to say that the strips are firstly shaped taking into account the final curvature to be obtained, then they undergo forming, and they are then fixed to each other on the tooling.

When there is a risk of the presence of liquids in the assembly 100, the ends of the strips 250, 252, 350 and 352 which are located lowest, have holes 160 and 162 to allow drainage of the liquids . In the embodiment of the invention presented in Figs. 1 to 3, the holes 160 and 162 are at the level of the first plate 102, but in another embodiment where the first plate 102 is above the second plate 104, the holes are made at the level of the second plate 104.

The holes 162, in addition to their function of passage for liquids to drain, also allow the increase in volume by making the different volumes communicate with each other.

[0068] FIG. 4 shows an assembly 400 constituting an acoustic insulator according to a second embodiment of the invention. Assembly 400 according to the second embodiment is similar to assembly 100 according to the first embodiment except that the hexagonal shapes are replaced by circular shapes.

Thus, the first structure 410 forms a honeycomb structure which comprises a succession of cages 402 each being hollow and having a circular section thus delimiting each a cylindrical cell. For a line, the first structure 410 consists of a first strip 450 and a second strip 452, which are arranged opposite one another and extend between the first plate and the second plate. For each cage 402, the first strip 450 is shaped to form half of the wall of said cage 402 which here takes the form of a semi-cylinder and the second strip 452 is shaped to form the other half of the wall of said cage 402 which here takes the form of a half-cylinder.

The junction walls also consist of two spaced apart sides from one another. In the second embodiment, the junction walls take the form of a cylinder arc.

The second structure 412 comprises a succession of cones 502 where the base of each cone 502 has a circular section and is positioned between the two strips 450 and 452 of the first structure 412. Each cone 502 forms a cone of revolution. The circular base has the same dimensions as the cell to accommodate it.

For a line, the second structure 412 consists of a first strip 550 and a second strip 552, which are arranged opposite one another and extend between the bases and the tops of the cones 502, that is to say between the first plate and the second plate. For each cone 502, the first strip 550 is shaped to form half of the wall of said cone 502 which here takes the form of a half-cone of revolution and the second strip 552 is shaped to form the other half of the wall of said cone 502 which here takes the form of a half-cone of revolution.

In the second embodiment, the connecting walls take the form of a cylinder arc.

Of course, it is also possible to provide that the circular or hexagonal sections are replaced by rectangular sections.

The possibilities of asymmetry of the cones and presence of the holes are applicable to all the embodiments.

Thus in general, each first structure 110, 410 comprises a succession of cages 202, 402, each delimiting a cell 205 having a section of a shape (hexagonal, circular, rectangular), and between two cages 202 , 402 neighbors, a junction wall 207 consisting of two sides spaced from each other.

In general, each second structure 112, 412 comprises a succession of cones 302, 502, each having a base and an apex, and between two neighboring cones 302, 502, a connecting wall 307 consisting of two sides , where the base has a section of the same shape as the section of the cells 205.

In general, each first structure 110, 410 consists of a first strip 250, 450 and a second strip 252, 452 arranged opposite one another and extend between the first plate 102 and second plate 104, where for each cage 202, 402, the first strip 250, 450 is shaped to form half of the wall of said cage 202, 402 and the second strip 252, 452 is shaped to form the 'other half of the wall of said cage 202, 402, and where for two successive halves, each strip 250, 252, 450, 452 has a section of the junction wall 207 which connects two consecutive halves. As the case may be, half of the wall of a cage 202, 402 is made up of three successive sides 204, or of a half-cylinder.

In general, each second structure 112, 412 consists of a first strip 350, 550 and a second strip 352, 552 arranged opposite one another and extend between the first plate 102 and second plate 104, where for each cone 302, 502, the first strip 350, 550 is shaped to form half of the wall of said cone 302, 502 and the second strip 352, 552 is shaped to form the other half of the wall of said cone 302, 502, where for each strip 350, 352, 450, 452, at least one of the wall halves of each cone 302, 502 is pierced with a hole 354, and where for two successive halves, each strip 350, 352, 450, 452 comprises a section of the connecting wall 307 which connects two consecutive halves. As the case may be, half of the wall of a cone 302, 502 consists of three successive sides 304, or of a half-cone of revolution.

In general, each cone 302, 502 is located in a cell 205 and each connecting wall 307 is located between the two sides of a junction wall 207, and between two neighboring first structures 110, 410, a second structure 112, 412 is also put in place.

Claims (1)

[Claim 1] Claims Assembly (100, 400) constituting an acoustic insulator and comprising a first plate (102), a second plate (104) pierced with holes (106), a plurality of first structures (110, 410) arranged one next to the other according to a second direction (203), and a plurality of second structures (112, 412) arranged one next to the other in the second direction (203), where each first structure (110, 410) comprises a succession of cages (202, 402), each delimiting a cell (205) having a cross section of a shape, and between two neighboring cages (202, 402), a junction wall (207) made up of two spaced apart sides, where each second structure (112, 412) comprises a succession of cones (302, 502), each having a base and an apex, and between two neighboring cones (302, 502), a connecting wall (307) consisting of two sections, where the base has a section of the same shape as the section of the cells (205), where each first structure (110, 410) consists of a first strip (250, 450) and a second strip (252, 452) arranged opposite one another and extend between the first plate (102) and the second plate (104), where for each cage (202, 402), the first strip (250, 450) is shaped to form half of the wall of said cage (202, 402) and the second strip (252, 452 ) is shaped to form the other half of the wall of said cage (202, 402), and where for two successive halves, each strip (250, 252, 450, 452) has a section of the junction wall (207) which connects two consecutive halves, where each second structure (112, 412) consists of a first strip (350, 550) and a second strip (352, 552) arranged opposite one another and s '' extend between the first plate (102) and the second plate (104), where for each cone (302, 502), the first strip (350, 550) is shaped to form half of the wall of said cone (302, 502 ) and the second strip (352, 552 ) is shaped to form the other half of the wall of said cone (302, 502), where for each strip (350, 352, 450, 452), at least one of the wall halves of each cone (302, 502 ) is pierced with a hole (354), and where for two successive halves, each strip (350, 352, 450, 452) has a section of the connecting wall (307) which connects two consecutive halves, so that each cone (302, 502) is located in a cell (205) and so that each connecting wall (307) is located between the two sides of a junction wall (207), and where between two first neighboring structures (110, 410), a second structure (112, 412) is also put in place. [Claim 2] Assembly (100, 400) according to claim 1, characterized in that at least one cone (302, 502) is asymmetrical, so that the volumes of the two chambers (150, 152) created between said cone (302, 502) and the wall of the cage (202, 402) where it is housed are different. [Claim 3] Assembly (100, 400) according to one of claims 1 or 2, characterized in that at least one of the ends of the strips (250, 252, 350, 352, 450, 452, 550, 552) has holes (160, 162). [Claim 4] Assembly (100) according to one of claims 1 to 3, characterized in that the shape is a hexagon, in that each half of the wall of a cage (202) consists of three successive sides (204), and in that each half of the wall of a cone (302) consists of three successive sides (304). [Claim 5] Assembly (400) according to one of claims 1 to 3, characterized in that the shape is a circle, in that each half of the wall of a cage (402) consists of a half-cylinder, and in that each half of the wall of a cone (502) consists of a half-cone of revolution. [Claim 6] Method of manufacturing an assembly (100) according to one of claims 1 to 3, comprising: a first step during which a first strip (350) of the second structure (112) is fixed to a first strip (250) of the first structure (110), a second step during which a second strip (352) of the second structure (112) is fixed to the first strip (350) of the second structure (112) thus fixed, - a third step during which a second strip (252) of the first structure (Π0) is fixed to the second strip (352) of the second structure (112) thus fixed, - as long as a first structure (110) or a second structure (112) must be added, a looping step on the first step considering that the second strip (252) of the first structure (110) thus fixed constitutes the first strip (250) of the following first structure (110), - a stage during which, the first and second structures (110, 112) thus fixed are fixed between the first plate (102) and the second plate (104).